Methods of making lithium selective nanofiltration membranes and their applications

A method of making a high-performance thin-film composite (TFC) nanofiltration (NF) membrane, the method comprising:

• (i) preparing a polysulfone (PSf) or polyethersulfone (PES) support membrane by using a non-solvent induced phase separation (NIPS) technique:
• (a) dissolving PSf or PES polymer in one or more solvents so as to form a uniform solution;
• (b) maintaining a concentration of polyvinylpyrrolidone in the uniform solution at a range of 1.0-5.0 wt %;
• (c) maintaining a concentration of polyethylene glycol in the uniform solution at a range of 2.0-10.0 wt %;
• (d) maintaining a concentration of acrylic acid in the uniform solution at a range of 2.0-10.0 wt %;
• (e) maintaining a concentration of surfactant in the uniform solution at a range of 2.0-10.0 wt %;
• (f) degassing the solution, and thereafter casting the solution on a 100-micron thick nonwoven polyester support at a cast thickness at about 0.10-0.12 mm to form a cast film;
• (g) immediately immersing the cast film in a water precipitation bath and initiating phase separation;
• (h) removing the solvents, and then treating the formed support membrane with a solution;
• (ii) contacting the formed support membrane with an aqueous diamine solution comprising 0.1-3% w/v piperazine, and 0.5-2.0% w/v NaOH, for a time period of 60-120 seconds;
• (iii) removing excess aqueous diamine solution from the support surface;
• (iv) gently pouring an organic solution containing 0.15% w/v TMC on the support surface and initiating an interfacial polymerization (IP) reaction;
• (v) draining the organic solution from the support surface and heat-curing the formed thin film composite (TFC) at about 80° C. for about 5 minutes;
• and
• (vi) washing the final thin-film composite (TFC) nanofiltration (NF) membrane.